#include<bits/stdc++.h>
using namespace std;
#define MOD 1000000007
#define PI 3.14159265
#define REP(i, a, b) \
for (int i = int(a); i < int(b); i++)
#define TRvi(c, it) \
for (vi::iterator it = (c).begin(); it != (c).end(); it++)
#define TRvii(c, it) \
for (vii::iterator it = (c).begin(); it != (c).end(); it++)
#define TRmsi(c, it) \
for (msi::iterator it = (c).begin(); it != (c).end(); it++)
typedef long long ll;
typedef vector<int> vi;
typedef pair<int, int> ii;
typedef vector<ii> vii;
typedef set<int> si;
typedef map<string, int> msi;


int main()
{
    int q,n,x,y;
    cin>>q;
    while(q--){
        bool x=true;
        cin>>n;
        ii a[n];
        REP(i,0,n){
            cin>>x>>y;
            a[i]=make_pair(x,y);
        }  
            REP(i,1,n)
                if(a[i].first!=a[0].first && a[i].second!=a[0].second){
                x=false;break;
            }
            if(x)cout<<"YES";
        else cout<<"NO";
        cout<<endl;
    }
    return 0;
}